This application claims priority to U.S. Provisional Application No. 60/759,550, the entire contents of which are incorporated herein by reference. Without limiting the scope of the invention, its background is described in connection with poly (arylene ether) copolymers, oligomers, cross-linked copolymers, multi-block copolymers, polymers, and membranes having hydrophilic regions and hydrophobic regions.